A CSCF (Call Session Control Function) is a functional entity in an internet protocol (IP) multimedia subsystem (IMS), and is mainly responsible for processing signaling control in a multimedia call session process. The CSCF may be classified into a P-CSCF (proxy CSCF), an I-CSCF (interrogating CSCF), and an S-CSCF (serving CSCF).
In a service control process, if the P-CSCF is faulty, and if a user terminal that registers with the P-CSCF is used as a called party, and the S-CSCF finds the P-SCCF fault when managing a called service, a user of the terminal cannot be contacted by using the P-CSCF, which causes a service failure.
In the prior art, two P-CSCFs form primary and secondary P-CSCFs, and when one P-CSCF is faulty, a service may be taken over by the secondary P-CSCF. A same IP address IP1 is configured for a P-CSCF1 and a P-CSCF2. Generally, the P-CSCF1 advertises a route of the P-CSCF1 to the outside, but the P-CSCF2 does not advertise an address of the P-CSCF2. First, the user terminal sends a registration request to the IP1 and registers with the primary P-CSCF1, and the P-CSCF1 backs up user registration information in the secondary P-CSCF2. When the P-CSCF1 is faulty, the P-CSCF2 can sense, by means of heartbeats, that the P-CSCF1 is faulty. In this case, the P-CSCF2 advertises a route of the P-CSCF2 to the outside, and then a service of the terminal is routed to the P-CSCF2 for processing. Because user information has been backed up during previous registration, the new P-CSCF2 can correctly process a request of the user.
In the prior art, main disadvantages of a data backup solution between primary and secondary network elements include: heartbeat detection is performed between a primary network element and a secondary network element, which is prone to a dual-host fault, causing a problem that neither the primary network element nor the secondary network element can perform a service. In addition, the primary network element and the secondary network element present a same IP to the outside, which requires support from a near-end router, where processing is relatively complex.